Given an integer

`n`

, you are asked to calculate the number of different bit-strings of length `n`

. Bit strings are strings that only have 0s and 1s. Input

The only line of the input contains a single integer

`n`

(1 ≤ n ≤ 30) Output

The program should print the number of bit strings of length

`n`

. Examples

Input | Output |

3 | 8 |

4 | 16 |

Explanation

3 → 000, 001, 010, 011, 100, 101, 110, 111 ⇒ 8 different bit-strings.

4 → 000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111 ⇒ 16 different bit-strings.